Counterbalance mechanism



0t.13,1'936. E E- HOWARD ET AL 2,057,028

COUNTERBALANCE MECHANI SM Oct. 13, 1936. E. E. HOWARD ETAI.

COUNTERBALANCE MECHANISM `2 sheets-sheet 2 Filed Bepi. 17, 1954 ATTORNEYPatented Oct. 13, 1936 UNITED STATES PATENT OFFICE COUNTERBALANCEMECHANISM Application September 17, 1934, Serial No. 744,340

10 Claims.

This invention relates to a counter-balance mechanism and particularlyto means for counter-balancing a movingrload such as, for example, avertical lift bridge wherein the weight of the span is counter-balancedthrough counterweights which are connected therewith by flexiblesuspending means operating over sheaves located on i'lxed members at theends of the span. j

In a counter-balance of this character, the suspending'cables playacross the sheaves from one side thereof to the other as the lift spanis raised and lowered. Consequently, there cannot be true or evenbalance during the entire up and down movement of the span andcounterweights for the reason that portions of the suspending cablesshift from one side of the sheaves to the other, thus throwing themechanism out of balance.

It is, therefore, the principal object of our invention to maintain anapproximately constant balance throughout the entire lift of a movingload regardless of the shifting'of the weight of the suspending cablesacross the sheaves.

In accomplishing this and other objects of the invention, as hereinafterpointed out, we have provided improved details ofstructure, thepreferred forms Vof .which are illustrated in the accompanying drawings,wherein: V

Fig. 1 is a diagrammatic perspective view of a lift bridge equipped witha counter-balance mechanism embodying the features of the presentinvention.

Fig. 2 is a cross sectional view through one of the towers at the end ofthe lift span particularly illustrating the means to compensate for theolbalancing effect of the suspending cables during raising and loweringof thelift span, the span being shown in lowered position.

Fig. 3 is' a similar cross section showing the position of the partswhen the span is about midway of raised position.

Fig. 4 is a horizontal section on the line 4-4, Fig. 3.

Fig. 5 is an enlarged detail perspective view of the anchor member whichconnects a pair of compensating cables with a main counterweight.

Fig. 6 is a modied form of compensating cable connection with a maincounter-weight.

Fig. '7 is a modied form of compensating cable arrangement.

Referring more in detail to the drawings:

l designates a conventional type of vertical lift bridge includingspaced towers 2 and 3 that are supported on piers or other suitablesubstructures 4 and 5 located on the respective sides of a river orother channel. Bridging the piers is a lift span 6 having its endsnormally resting on the sub-structure so that the floor 'I thereof Ylies in the plane of the oors 8 and 8 of the bridge at the towers 2 and3. In the bridge illustrated, the span 6 is raised above lthe bridgefloor level and lowered by mechanism including pairs of main sheaves9-l0 and |I,-|2 located at the sides of the respective towers in linewith the corners of the lift span.

Operating over the pairs of main sheaves are sets of suspending cablesI3|4 and |5--I6 each set of cables having its ends l1 depending from thesheaves and connected to the adjacent corners of the lift span and theopposite ends I8 thereof connected to the main counter-weights I9 and 20so that when the sheaves are rotated the suspending cables will raisethe lift span and lower the counter-weights within the respectivetowers.

In the bridge illustrated, the main sheaves are actuated by suitablemachinery located on the respective towers as indicated at 2| to drivegears 22 and 23 operably connected with the shafts 24 of the sheaves.

When the lift span is in lowered position as shown in Fig. 1, the lengthof suspending cables depending from the span side of the sheaves issubstantially greater than the length of suspending cables dependingfrom the counterweight side of the sheaves. When' the lift span israised to its highest position, the length of suspending cablesdepending from the span side of the sheaves is substantially less thanthe length of suspending cables depending from the counterweight side ofthe sheaves.V

Due to the shifting of portions of the suspending cables from the spanside of the sheaves to the counter-weight side of the sheaves during theraising of the span, there can be a true balance of all the movingelements on the two sides of the sheaves for only one single position ofthe span. Y

In accordance with the present invention, we provide a compensatingapparatus to automatically compensate for the shifting of the cables andto provide an approximate true balance for all positions of the span.

' Located on the respective sides of each tower are pairs of pulleys25-26 and 21-28 which are preferably mounted on counter-shafts 35 and 36arranged with their axes of rotation in the longitudinal direction oftheVV bridge and rotatably mounted in bearings 31 and 38 xed to theframe work of the towers. The pulleys are f spacedY apart a distanceslightly greater than the width of the counter-weightsY I9 and 20, toalign with anchors 39'which' are fixed to the sides of thecounter-weights midway between ture of the segments, the' groovesterminate in V'compensating cables 49v and 50.

tangential apertures 44 and 44' extending through to a recess 45provided atV the intersection of Vthe arcuate portions to provide stopshoulders 46. VExtending through the respective Y apertures 44 and 44 ofeach anchor and having their ends secured-by socket members 4lY and 48which iengage thestop shoulders is a pair of The pair of compensatingcables 49 and 50 operateover the aligning pulleys and suspend auxiliaryweights 5|'and 52.

The aligning pulleys are preferably located so that the portions of thecompensating cables extending-between the'serpulleys and the anchors onYthe main counter-weights are in a horizontal plane when the lift spanis at midpoint of up and down movement.

' With the aligningpulleys so located, the aux- VViliaryweights have acombined weight such that the vertical component of the pull of all ofthe compensating cables on the anchors on the main counterweights whenthe span is in its lowest position is substantially equal to the weightof that portionV of the suspending cables whichfwill sheaves.

Y be paid over the sheaves during the movement of the span to itshighestposition. l

When the liftA span is in lowered position,v the compensating cablesareengaged in the grooves 43 ofthe lower'segments-of the anchors andtheauxiliaryweights .at the ends thereof are suspended in close relation tothe pulleys so v that the auxiliary weights are effective incompensating for the greater length and weight of the suspending cableson the span side of Vthe main It is evident-that the downward pull onthe main counter-weights exerted by the auxiliary weights is thevertical component of the pull in Ythe compensating cables, which pullis at its maximum when the main counter-weights are at the upper-mostposition andthe bridge is in lowered position. Y Y

As the span'is lifted and the main counterweights descend, the verticalcomponent decreases in amounts proportional'to thelvarying Vangularityof the compensatingcables between pulleys andthe anchors until thecompensating cables are in a horizontal plane.V y

In this position, the vertical components become .zero andthe auxiliaryweights have no influence upon the main counter-weights.CorrespOndingly, as the main counter-weights descend a downward orupward pull, thereby providing substantially true counter-balancingofthe entire assembly throughout the range of movement of the span.

The horizontal components of the compensating cables are taken care ofby the strength of the frame work comprising the towers; however,

it will be'noted that due to the fact that the auxiliary weights andtheir cables are carried by (the towers there are no lateral externalloads tional weight added to the lift span because of the compensatingmechanism. Also, due to theprovision of the auxiliary v counter-weightsin pairs, the horizontal components of their'compensating cables balanceeach other and do not tend to .shift the main counterweights out oftheir normal path of travel.

Whilethe location of the aligning pulleys at the point above describedis most desirable for the preferred condition of balancing, vsuchalocation may at times be inconvenient or impractical andaI suiiicientlyY satisfacory degree fof compensation may be secured by shifting thelocation. o f the aligning pulleys. These aligning pulleysmay underextreme conditions be so located-with relation to the anchors on themain counterweights that the compensating cablesr provide only an upwardpull on the main counter-weights for all positions of the span, or sothat they provide only a downward pull for all positions of the span.For such alternate locations, it may be desirable to have the maincounter-weight greater Vor less in weight than the lift span.

the ends of the 'compensating cables areprovided with socket members53'having sleeve-portions 54 pivotally mounted' on a'bolt 55 that is''secured to the side face of the .main counter-weight.

As illustrated inFig. .'7, our ,invention contemplates that it mayattimes be desirableV to providejpulleys 56 and"5`lV on the maincounterweight instead of a xed anchor and to pass the compensatingcables around the pulleys and carry them back to fixed connections 58and 5,9 on theV towers. s

, By such means, Vthe Weightfof the auxiliary weights may be reduced byone-half of the weight required for their arrangement in the preferredform of the invention, but the amount of ,vertical movement oftheauxiliary weights would be correspondingly doubled, thereby impartingthe same force on lthe counter-weights. s Y

` It also may be desirable to mount several pulf pending cables passingacross-the sheaves durin the movement of the span.

While We have particularly described the invention as associated with alift bridge, it is obvious that the compensating principle may beapplied to various other structures having parts which are moved up anddown inthe manner of a lift bridge and We do not wish to be limited tothe particular combination of the compensating means with thecounter-balancing mechanism of a lift bridge.

It is also apparent that the compensating mechanism may have differentrelative position with relation to the sides and ends of thecounterweights without departing from the spirit of the invention.

What we claim and desire to secure by Letters Patent is:

1. In combination with a structure having a part arranged to movevertically, and a counterbalance weight for said part, supplementarymeans for said counter-balance weight including a constant supplementaryweight, a pulley mounted on said structure laterally of saidcounterbalance weight, and eXible means acting over said pulley andconnecting the supplementary weight with the counter-balance weight.

2. In an apparatus of the character described including Xed and movablemembers, sheaves carried by the xed member, a counter-balance weight,cables operating over the sheaves and having ends connected to themovable member and to said counter-balance weight, pulleys carried bythe fixed member at opposite sides of said counter-balance weight,flexible members operating over said pulleys and having connection withsaid counter-balance weight, and constant auxiliary weights connected tosaid flexible members for imparting forces to said Weight havingvariable components varying substantially in proportion to pay of thecables across said sheaves.

3. In a lift bridge including a lift span and iiXed towers at therespective ends of the span, sheaves on the towers, cables operatingover the sheaves and having ends connected to the ends of the span,counter-balance weights suspended from the opposite ends of the cables,pairs of pulleys carried by the towers at opposite sides of thecounter-balance weights, pairs of flexible members operating over saidpulleys and having portions connected with the counter-balanceV weights,and auxiliary weights connected to the ends of said flexible members forimparting forces to said counter-balance weights having verticalcomponents varying substantially in proportion to pay of the cablesacross said sheaves.

4. In a lift bridge including a lift span and towers at the respectiveends of the span, sheaves carried by the towers, counter-balance weightsfor each end of the span, cables operating over the sheaves and havingends connected to the lift span and to said counter-balance weights,pulleys carried on the towers with their axes arranged at right anglesto the axis of the sheaves, iiexible members operating over said pulleysand having portions connected with said counterbalance weights, andconstant auxiliary weights connected to ends of said iiexible membersfor imparting forces to said counter-balance weights having variablecomponents varying substantially in proportion to pay of the cablesacross said sheaves.

5. In combination with relatively stationary and vertically movablemembers, primary means supported by the stationary member forcounterbalancing the vertically movable member, :guiding means onthestationary member, and supplementary counter-balancing means including.ilexible means connected with the primary counter-balancing meansY at apoint laterally spaced from the guiding means and movable over saidguiding means onthe stationary member, and constant weights freelysuspended by said ilexible means whereby variable forces are applied tothe primary counter-balancing meansv by the supplementarycounter-balance' means -in response to movement ofrsaid primary means.

6. In combination with relatively stationary and movable members, aweight supported by the stationary member for counter-balancing themovable member, an anchor member on the counter-balancing weight, pairedguides at intermediate points on the stationary member and spacedlaterally-from said anchor member, a pair of constant supplementaryweights, and means movable over said guides and connecting the pairedsupplementary weights with said anchor member to freely suspend saidsupplementary weights, whereby resultants of all forces applied by saidsupplementary weights to said counterbalance weightare variableincidental to movement of the counter-balance weight.

7. In combination with a lift bridge including spaced towers, a liftspan vertically movable between said towers and counter-balance weightsfor said span, paired constant supplementary weights, ilexible meansconnecting the supplementary weights with the counter-balancing weights,and means spaced laterally of the points of connection of the flexiblemeans with the counter-balance weights and at intermediate, verticalpositions on the towers for guiding the ilexible means tofreely suspendsaid supplementary weights, whereby forces applied by said supplementaryweights are caused to impart variable forces on the counter-balanceweights incidental to movement of the counter-balance weights.

8. In combination with a lift bridge including spaced towers and aY liftspan movable vertically between the towers, counter-balance weightsconnected with the span and vertically movable within the towers, pairedguide members arranged at intermediate, vertical positions on oppositesides of the towers, supplementary weights, paired flexible means runover said guide members and connecting the supplementary weights withthe counter-balance Weights at intermediate transverse points on thecounter-balance weights, whereby variable forces are applied to thecounter-balance weights by the supplementary weights in response tomovement of said counterbalance weights.

9. In combination with a lift bridge including spaced towers and a liftspan movable vertically between the towers, sheaves on the upper ends ofthe towers, primary counter-balance weights in the towers havingflexible connections run over said sheaves and connected with said span,anchor members on opposite sides of and arranged at intermediatetransverse positions on the primary weights, paired guide members atintermediate positions on the sides of the towers, supplementarycounter-balance weights and ilexible members run over said guide membersand connecting the supplementary weights with the anchor members on theprimary counter-balance Weights, whereby variable forces are applied tothe primary counter-balancing weights by the supplementarycounter-balance weights in response to movement of said primary Weightswhen the primary Weights move vertically in the towers above and belowsaid guide members.

' 10. In combination with spaced towers and a lift span verticallymovable between the towers, counter-balance weights flexibly spportedfrom and movable vertically along the towersfguide members at oppositesides of each of the towers,

` and paired, supplementary counter-balance memplanes extendingthrough'the axes offs'ad guide members, whereby progressivelyvariablellateral and vertical stresses are applied Vto the primarycounter-balance weights by thesuppl'ementary counter-balance WeightsVproportional to'vvaria'tion in lifting forces of the primaryweights andtheir connectors incident to` inverse travel of the `span andprimaryweights. Y Y Y Y Y Y ERNEST E. HOWARD.V

HENRY C. TAMMEN.

